1. Field of Invention
This invention relates generally to air diffusers which supply conditioned air to rooms. More specifically, this invention provides an air diffuser having a fixed area primary outlet and a secondary outlet having an area which is variable to increase with increased air flow rate through the diffuser.
2. Description of the Related Art
In order to achieve a desired indoor environment, an effective supply of conditioned air is required. Various types of air diffusing equipment, commonly known as diffusers, have been developed to supply this conditioned air to rooms. The performance of a diffuser is determined by its throw, which is the distance from the diffuser outlet to the location in the room where the diffuser velocity has decreased to a specified value. The proper throw must be maintained in order to adequately mix the air and to produce proper ventilation and thermal conditions in the room. However, achieving the proper throw can be difficult if the air flow rate through the diffuser is variable. Variable air flow results from the use of a variable air volume system. A variable air volume system has a control system which varies the air flow rate to match the changes in the cooling or heating requirement of an indoor environment. As the heating or cooling requirement is reduced, the air flowrate is correspondingly reduced, and vice versa.
Conventional air diffusers supply conditioned air through a constant area outlet. If the flow rate through such an outlet decreases, the throw distance is reduced. If the throw distance is reduced, it is difficult to maintain the desired ventilation and temperature distribution. Also, in cold air distribution systems, if the throw distance is reduced to less than the separation distance of the outlet jet of the diffuser, the outlet jet can separate or dump, causing thermal comfort problems.